In all other groups, there is a gap of one letter as in the alphabet between second and third letters.

In all other groups, there is a gap of two letters as in the alphabet between the second and the third letters.

In all other groups, there is a gap of one letter between first and third letters.

Except option (d), all letters in pairs having difference of four.

Except option (d), all letters in options having same difference among them.

8 + 3 = 11 ; 1 + 3 = 4
7 + 3 = 10 ; 3 + 3 = 6 ? 5

Except 8-15, in all the option, both of the numbers are the squares of consecutive natural numbers.

All other except '525' are cubes of some numbers.

In all other groups, last number between first and second letters is twice the sum of positions of first and last letters in the alphabet.

Except 'Garden' all the others are the parts of a tree.